Van Dyke brown
Van Dyke brown is a classic color, named after the Flemish painter Anthony Van Dyck. The color is also known as cassel earth and cologne earth. The material traditionally used for the pigment is brown peat or soil, which contains iron and manganese oxides and lignite. The inorganic parts of the pigment are fully lightfast while the organic part, lignite, is not. Therefore, the pigment is not very lightfast, it fades in sunlight.
I wrote “traditionally used” because pretty much all manufacturers fake the color nowadays, only a few have genuine goods. The most common way to mix the color is with black + brown, some manufacturers even add a little yellow to it. Samples of transparency, staining, and so on are not relevant because all manufacturers have different recipes to achieve their vision of the color, different mixtures of pigments are used to achieve the perfect Van Dyke brown color.
You probably have a brown color, maybe even a black one. Mix them (mostly brown, just a little black) and you have created a color that most manufacturers call Van Dyke brown
Of the larger manufacturers, there are only two that still use a real pigment for the color:
SHINHAN: Vandyke brownNBr8
HOLBEIN: Van Dyke Brown NBr8
Buy some of these if you really want the color, ignore all mixed colors from other manufacturers. Be aware that the color has limitations in terms of lightfastness.
Color index name: NBr8
Lightfastness: Not so good
Transparency: Semi transparent